During the 1970s, the proportion of high school graduates entering college each year hovered around 50 percent to 52 percent, but it has been rising for the past several years, reaching 55 percent in 1984 and jumping to 58 percent in 1985.

Vance Grant, a spokesman for the Education Department's Center for Statistics, said the reasons for the trend are not known, but he said one theory, based on surveys of student attitudes, is that students today ''are success-oriented. One way to get ahead is to go to college. They major in applied fields like business, engineering and health professions. And the opportunity is there. There are lots of grants, lots of scholarships and lots of community colleges where you can get an education in your own community.'' The Labor Department study found that there were nearly 2.7 million 1985 high school graduates and that more than 1.5 million were enrolled in college in October 1985 -- about 58 percent -- with women slightly outnumbering men. For blacks, the proportion going to college was 42 percent.

The study found that of the approximately 1.1 million graduates who did not enroll in college, 699,000 had jobs.

For black graduates the rate was lower, with 34 percent employed; for Hispanics, the figure was 42 percent.

Another 228,000 of the 1.1 million were seeking employment but could not find jobs. The author said the number of graduates unable to find jobs has been rising somewhat in recent years, probably reflecting increasing demands by employers for better-educated workers.